Mechanical function of the annulus fibrosus is preserved following quasi-static compression resulting in endplate fracture

Bilayer annulus fibrosus specimens were mechanically characterized using CellScale soft-tissue testing systems under hydrated conditions. Uniaxial tensile testing was performed on a CellScale BioTester equipped with 0.7 mm tungsten rakes. Samples were preconditioned with three loading cycles to 10% strain and subsequently stretched to 50% strain at a strain rate of 1%/s while submerged in phosphate-buffered saline. Force–displacement data were used to generate stress–strain curves and calculate Young’s modulus for superficial and mid-span annular layers. In addition, interlamellar adhesion was quantified using 180° peel tests performed on a CellScale UStretch system, enabling direct assessment of lamellar bonding strength following endplate fracture. Together, these CellScale-based measurements demonstrated preservation of annulus fibrosus tensile and interlamellar mechanical function despite endplate injury.